Which statement best describes the force of gravity

Gravity is measured by the acceleration that it gives to freely falling objects. At Earth's surface the acceleration of gravity is about 9.8 metres (32 feet) per second per second.

B is the answer because the area between the velocity time graph and the x-axis is the distance traveled. If you look at the velocity time graph from 0-2, seconds you will see an area of 40m. Only choice B matches that at 2 seconds, the distance traveled is 40m. You can go on to confirm the remaining trip matches that of B by calculating the 2-4 seconds of the velocity time graph area between the x-axis and graph as -40m (negative because area is under the x-axis). Again, it matches graph B, showing that the total distance traveled is 0 for the entire trip.